The exhaust gas sensors shown there have, on their end exposed to the exhaust gas, an outer and an inner protective tube that surround a ceramic sensor element. The protective tubes are shaped so that a guide flow occurs in which the sensor element is protected on the one hand from the impact of liquid components of the exhaust gas, such as water drops, and on the other hand there takes place a flow over a measurement area of the sensor element, essentially in the longitudinal direction of the sensor.
Due to the long path of the exhaust gas inside the protective tubes, and due to the rather low interaction of the exhaust gas with the measurement area of the sensor element when flowing over it in the longitudinal direction, such exhaust gas sensors are provided in particular for installation in exhaust gas trains of internal combustion engines and burners in which there is a relatively high flow speed, and/or in applications in which the demands on the dynamics of the measurement devices are rather low.
On the other hand, however, there is a need for exhaust gas sensors that can also perform measurements with good dynamic behavior even in the exhaust gas trains of internal combustion engines and burners in which there is only a low flow speed. For example, such sensors, fashioned as soot sensors and installed in an exhaust gas box of a commercial vehicle, are intended to collect a minimum quantity of soot within a specified time period, so that a precise measurement of the quantity of soot emitted by the internal combustion engine of the commercial vehicle is possible.